Electrosurgical apparatus with real-time rf tissue energy control

ABSTRACT

A radio-frequency (RF) amplifier having a direct response to an arbitrary signal source to output one or more electrosurgical waveforms within an energy activation request, is disclosed. The RF amplifier includes a phase compensator coupled to an RF arbitrary source, the phase compensator configured to generate a reference signal as a function of an arbitrary RF signal from the RF arbitrary source and a phase control signal; at least one error correction amplifier coupled to the phase compensator, the at least one error correction amplifier configured to output a control signal at least as a function of the reference signal; and at least one power component coupled to the at least one error correction amplifier and to a high voltage power source configured to supply high voltage direct current thereto, the at least one power component configured to operate in response to the control signal to generate at least one component of the at least one electrosurgical waveform.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical apparatuses, systemsand methods. More particularly, the present disclosure is directed to anelectrosurgical generator adapted for real-time adjustment of itsoutput.

2. Background of Related Art

Energy-based tissue treatment is well known in the art. Various types ofenergy (e.g., electrical, ultrasonic, microwave, cryogenic, heat, laser,etc.) are applied to tissue to achieve a desired result. Electrosurgeryinvolves application of high radio frequency electrical current,microwave energy or resistive heating to a surgical site to cut, ablate,coagulate or seal tissue.

In bipolar electrosurgery, one of the electrodes of the hand-heldinstrument functions as the active electrode and the other as the returnelectrode. The return electrode is placed in close proximity to theactive electrode such that an electrical circuit is formed between thetwo electrodes (e.g., electrosurgical forceps). In this manner, theapplied electrical current is limited to the body tissue positionedbetween the electrodes.

Bipolar electrosurgical techniques and instruments can be used tocoagulate blood vessels or tissue, e.g., soft tissue structures, such aslung, brain and intestine. A surgeon can either cauterize,coagulate/desiccate and/or simply reduce or slow bleeding, bycontrolling the intensity, frequency and duration of the electrosurgicalenergy applied between the electrodes and through the tissue. In orderto achieve one of these desired surgical effects without causingunwanted charring of tissue at the surgical site or causing collateraldamage to adjacent tissue, e.g., thermal spread, it is necessary tocontrol the output from the electrosurgical generator, e.g., power,waveform, voltage, current, pulse rate, etc.

In monopolar electrosurgery, the active electrode is typically a part ofthe surgical instrument held by the surgeon that is applied to thetissue to be treated. A patient return electrode is placed remotely fromthe active electrode to carry the current back to the generator andsafely disperse current applied by the active electrode. The returnelectrodes usually have a large patient contact surface area to minimizeheating at that site. Heating is caused by high current densities whichdirectly depend on the surface area. A larger surface contact arearesults in lower localized heat intensity. Return electrodes aretypically sized based on assumptions of the maximum current utilizedduring a particular surgical procedure and the duty cycle (i.e., thepercentage of time the generator is on).

Conventional electrosurgical generators operate in one operational mode(e.g., cutting, coagulation, spray, etc.) which is set prior tocommencement of the procedure during a given activation period. Ifduring treatment a need arises to switch form one mode to another, suchas during a cutting procedure when a vessel is cut and begins to bleed,the first mode (e.g., cutting) is terminated manually and the secondmode (e.g., coagulation) is switched on. There is a need for anelectrosurgical generator which can switch between a plurality of modesautomatically in response to sensed tissue and/or energy feedbacksignals.

SUMMARY

A radio-frequency (RF) amplifier for outputting at least oneelectrosurgical waveform is disclosed. The RF amplifier includes a phasecompensator coupled to an RF arbitrary source, the phase compensatorconfigured to generate a reference signal as a function of an arbitraryRF signal from the RF arbitrary source and a phase control signal; atleast one error correction amplifier coupled to the phase compensator,the at least one error correction amplifier configured to output acontrol signal at least as a function of the reference signal; and atleast one power component coupled to the at least one error correctionamplifier and to a high voltage power source configured to supply highvoltage direct current thereto, the at least one power componentconfigured to operate in response to the control signal to generate atleast one component of the at least one electrosurgical waveform.

In another embodiment, an RF amplifier configured to output at least oneelectrosurgical waveform in response to an arbitrary RF signal isdisclosed. The RF amplifier includes a phase compensator coupled to anRF arbitrary source, the phase compensator configured to generate areference signal as a function of an arbitrary RF signal from the RFarbitrary source and a phase control signal; at least one errorcorrection amplifier coupled to the phase compensator, the at least oneerror correction amplifier configured to output a control signal atleast as a function of the reference signal; at least one powercomponent coupled to the at least one error correction amplifier, the atleast one power component configured to operate in response to thecontrol signal to generate at least one component of the at least oneelectrosurgical waveform; at least one current sensor configured tomeasure current of the at least one electrosurgical waveform and tooperate with the at least one power component to output a currentcontrol signal as a function of the measured current; a patientisolation transformer coupled to the RF amplifier, the patient isolationtransformer including a primary winding coupled to the at least onepower component, wherein the patient isolation is the only isolationcoupling component for delivering the at least one electrosurgicalwaveform to a patient and is configured to operate in a phase-correlatedmanner with the at least one electrosurgical waveform of the RFamplifier; and a high voltage power source configured to supply highvoltage direct current to the RF amplifier.

In embodiments, an electrosurgical generator is disclosed. The generatorincludes a high voltage power source configured to supply high voltagedirect current; an RF arbitrary source configured to generate anarbitrary RF signal; and a radio-frequency (RF) amplifier configured tooutput at least one electrosurgical waveform. The RF amplifier includes:a phase compensator coupled to the RF arbitrary source, the phasecompensator configured to generate a reference signal as a function ofthe arbitrary RF signal from the RF arbitrary source and a phase controlsignal; at least one error correction amplifier coupled to the phasecompensator, the at least one error correction amplifier configured tooutput a control signal at least as a function of the reference signal;and at least one power component coupled to the at least one errorcorrection amplifier and to the high voltage power source, the at leastone power component configured to operate in response to the controlsignal to generate at least one component of the at least oneelectrosurgical waveform. The generator also includes a controllerconfigured to adjust at least one of the arbitrary RF signal and thephase control signal in response to at least one selectedelectrosurgical operational mode.

According to another embodiment of the present disclosure, anelectrosurgical generator is disclosed. The generator includes a highvoltage power source configured to supply high voltage direct current;an RF arbitrary source configured to generate an arbitrary RF signal;and one or more radio-frequency (RF) amplifiers configured to output atleast one electrosurgical waveform. The radio-frequency (RF) amplifiersinclude: a phase compensator coupled to the RF arbitrary source, thephase compensator configured to generate a reference signal as afunction of the arbitrary RF signal from the RF arbitrary source and aphase control signal; a first control loop and a second control loop.The first control loop includes a first error correction amplifiercoupled to the phase compensator, the first error correction amplifierconfigured to output a first control signal at least as a function ofthe reference signal and a first power component coupled to the firsterror correction amplifier and to the high voltage power source, thefirst power component configured to operate in response to the firstcontrol signal to generate a first component of the at least oneelectrosurgical waveform. The second control loop includes a seconderror correction amplifier coupled to the phase compensator, the seconderror correction amplifier configured to output a second control signalat least as a function of the reference signal; and a second powercomponent coupled to the second error correction amplifier and to thehigh voltage power source, the second power component configured tooperate in response to the second control signal to generate a secondcomponent of the at least one electrosurgical waveform. The generatoralso includes a controller configured to adjust at least one of thearbitrary RF signal and the phase control signal in response to at leastone selected electrosurgical operational mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein withreference to the drawings wherein:

FIG. 1 is a schematic block diagram of an electrosurgical systemaccording to one embodiment of the present disclosure;

FIG. 2 is a front view of an electrosurgical generator according to anembodiment of the present disclosure;

FIG. 3 is a schematic block diagram of the electrosurgical generator ofFIG. 2 according to an embodiment of the present disclosure; and

FIG. 4 is a schematic block diagram of a radio frequency amplifier ofthe electrosurgical generator of FIG. 3 according to an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail.

The generator according to the present disclosure can perform monopolarand/or bipolar electrosurgical procedures, including vessel sealingprocedures. The generator may include a plurality of outputs forinterfacing with various electrosurgical instruments (e.g., a monopolaractive electrode, return electrode, bipolar electro surgical forceps,footswitch, etc.). Further, the generator includes electronic circuitryconfigured for generating radio frequency power specifically suited forvarious electrosurgical modes (e.g., ablation, coagulation, cutting,blending, division, etc.) and procedures (e.g., monopolar, bipolar,vessel sealing).

FIG. 1 is a schematic illustration of a bipolar and monopolarelectrosurgical system 1 according to one embodiment of the presentdisclosure. The system 1 includes one or more monopolar electrosurgicalinstruments 2 having one or more electrodes (e.g., electrosurgicalcutting probe, ablation electrode(s), etc.) for treating tissue of apatient. Electrosurgical energy is supplied to the instrument 2 by agenerator 20 via a supply line 4 that is connected to an active terminal30 of the generator 20, allowing the instrument 2 to coagulate, ablateand/or otherwise treat tissue. The energy is returned to the generator20 through a return electrode 6 via a return line 8 at a return terminal32 of the generator 20. The system 1 may include a plurality of returnelectrodes 6 that are arranged to minimize the chances of tissue damageby maximizing the overall contact area with the patient. In addition,the generator 20 and the return electrode 6 may be configured formonitoring so-called “tissue-to-patient” contact to insure thatsufficient contact exists therebetween to further minimize chances oftissue damage.

The system 1 may also include a bipolar electrosurgical forceps 10having one or more electrodes for treating tissue of a patient. Theelectrosurgical forceps 10 includes opposing jaw members having one ormore active electrodes 14 and a return electrode 16 disposed therein.The active electrode 14 and the return electrode 16 are connected to thegenerator 20 through cable 18 that includes the supply and return lines4, 8 coupled to the active and return terminals 30, 32, respectively.The electrosurgical forceps 10 is coupled to the generator 20 at aconnector 60 or 62 (FIG. 2) having connections to the active and returnterminals 30 and 32 (e.g., pins) via a plug (not shown) disposed at theend of the cable 18, wherein the plug includes contacts from the supplyand return lines 4, 8.

With reference to FIG. 2, the generator 20 may be any suitable type(e.g., electrosurgical, microwave, etc.) and may include a plurality ofconnectors 50-62 to accommodate various types of electrosurgicalinstruments (e.g., multiple instruments 2, electrosurgical forceps 10,etc.). With reference to FIG. 2, front face 40 of the generator 20 isshown. The generator 20 includes one or more display screens 42, 44, 46for providing the user with variety of output information (e.g.,intensity settings, treatment complete indicators, etc.). Each of thescreens 42, 44, 46 is associated with a corresponding connector 50-62.The generator 20 includes suitable input controls (e.g., buttons,activators, switches, touch screen, etc.) for controlling the generator20. The display screens 42, 44, 46 are also configured as touch screensthat display a corresponding menu for the electrosurgical instruments(e.g., multiple instruments 2, electrosurgical forceps 10, etc.). Theuser then makes inputs by simply touching corresponding menu options.

The generator 20 is configured to operate in a variety of modes. In oneembodiment, the generator 20 may output the following modes, cut, blend,division with hemostasis, fulgurate and spray. Each of the modesoperates based on a preprogrammed power curve that dictates how muchpower is output by the generator 20 at varying impedance ranges of theload (e.g., tissue). Each of the power curves includes power, voltageand current control range that are defined by the user-selected powersetting and the measured minimum impedance of the load.

In the cut mode, the generator 20 may supply a continuous sine wave at apredetermined frequency (e.g., 472 kHz) having a crest factor of about1.5 with an impedance of from about 100Ω to about 2,000Ω. The cut modepower curve may include three regions: constant current into lowimpedance, constant power into medium impedance and constant voltageinto high impedance. In the blend mode, the generator may supply burstsof a sine wave at the predetermined frequency, with the burstsreoccurring at a first predetermined rate (e.g., about 26.21 kHz). Inone embodiment, the duty cycle of the bursts may be about 50%. The crestfactor of one period of the sine wave may be about 1.5. The crest factorof the burst may be about 2.7.

The division with hemostasis mode may include bursts of sine waves at apredetermined frequency (e.g., 472 kHz) reoccurring at a secondpredetermined rate (e.g., about 28.3 kHz). The duty cycle of the burstsmay be about 25%. The crest factor of one burst may be about 4.3 acrossan impedance of from about 100Ω to about 2,000Ω. The fulgurate mode mayinclude bursts of sine waves at a predetermined frequency (e.g., 472kHz) reoccurring at a third predetermined rate (e.g., about 30.66 kHz).The duty cycle of the bursts may be about 6.5% and the crest factor ofone burst cycle may be about 5.55 across an impedance range of fromabout 100Ω to about 2,000Ω. The spray mode may include bursts of sinewave at a predetermined frequency (e.g., 472 kHz) reoccurring at afourth predetermined rate (e.g., about 21.7 kHz). The duty cycle of thebursts may be about 4.6% and the crest factor of one burst cycle may beabout 6.6 across the impedance range of from about 100Ω to about 2,000Ω.

The screen 46 of FIG. 2 controls bipolar sealing procedures performed bythe forceps 10 that may be plugged into the connectors 60 and 62. Thegenerator 20 outputs energy through the connectors 60 and 62 suitablefor sealing tissue grasped by the forceps 10. The screens 42 and 44control monopolar output and the devices connected to the connectors 50and 56. The connector 50 is configured to couple to the instrument 2 andthe connector 52 is configured to couple to a foot switch (not shown).The foot switch provides for additional inputs (e.g., replicating inputsof the generator 20 and/or instrument 2). The screen 44 controlsmonopolar and bipolar output and the devices connected to the connectors56 and 58, respectively. Connector 56 is configured to couple to theinstrument 2, allowing the generator 20 to power multiple instruments 2.Connector 58 is configured to couple to a bipolar instrument (notshown). When using the generator 20 in monopolar mode (e.g., withinstruments 2), the return electrode 6 is coupled to the connector 54,which is associated with the screens 42 and 44. The generator 20 isconfigured to output the modes discussed above through the connectors50, 56, 58.

FIG. 3 shows a system block diagram of the generator 20 configured tooutput electrosurgical energy. The generator 20, a controller 24, a highvoltage DC power supply 27 (“HVPS”), a radio frequency amplifier 28,including an RF amplifier 28 a and an RF amplifier 28 b, includes aradio frequency (RF) arbitrary source 34, a sense processor 36, and apatient isolation transformer 38 including a primary winding 38 a and asecondary winding 38 b.

The HVPS 27 of FIG. 3 is configured to output high DC voltage from about15 V DC to about 200 V DC and is connected to an AC source (e.g.,electrical wall outlet) and provides high voltage DC power to the RFamplifier 28, which then converts high voltage DC power into radiofrequency energy and delivers the energy to the terminals 30 and 32,which are, in turn, coupled to the connectors 50-62 for supplying energyto the instrument 2 and the return pad 6 or the forceps 10. The HVPS 27is coupled to the RF amplifiers 28 a and 28 b and provides DC energythereto in a transparent manner to the operation of the RF amplifiers 28a and 28 b. In particular, the controller 24 provides an HVPS controlsignal to drive the positive and negative potentials of the HVPS 27 foreach of the RF amplifiers 28 a and 28 b with sufficient power to allowfor uninhibited operation of the RF amplifiers 28 a and 28 b. In otherwords, the controller 24 may control the RF amplifiers 28 a and 28 b viathe RF arbitrary source 34 or directly without adjusting the HVPS 27.

The RF arbitrary source 34 may be any RF signal generator such as avoltage controlled oscillator, a direct digital synthesizer, or anysuitable frequency generator configured to generate arbitrary waveformsfrom a fixed frequency reference clock. As herein, the term “arbitrary”denotes an RF signal that may be any arbitrarily defined waveform, e.g.,any frequency, amplitude, duty cycle, etc. The RF arbitrary source 34supplies an RF signal to the RF amplifiers 28 a and 28 b. Inembodiments, the RF signal may be a bipolar two-quadrant sinusoidalarbitrary RF signal. The RF amplifiers 28 a and 28 b process the RFarbitrary source signal and generate a differential RF drive signal tothe patient isolation transformer 38. RF output parameters, such asoperating RF power, voltage and current amplitude, operating frequency,gain parameters, phase compensation, time dependent configuration of theRF arbitrary source 34, are processed by the RF amplifiers 28 a and 28 bto deliver prescribed RF clinical treatment energy to achieve a desiredtissue effect.

The RF amplifier 28 a and RF amplifier 28 b are coupled to the primarywinding 38 a of the patient isolation transformer 38. The RF amplifier28 a is configured to output a positive half-cycle having a phase anglefrom about 0° to about 180° and the RF amplifier 28 b is configured tooutput a negative half-cycle having a phase angle from about 0° to about−180°. Thus, while the RF amplifier 28 a is providing sourcing RFcurrent (e.g., outputs positive current), the RF amplifier 28 b isproviding sinking current (e.g., outputs negative current). Conversely,while the RF amplifier 28 b is providing sourcing RF current (e.g.,outputs positive current), the RF amplifier 28 a is providing sinkingcurrent (e.g., outputs negative current).

The patient isolation transformer 38 combines the differential RF driveoutput of the RF amplifiers 28 a and 28 b to deliver phase correlated RFenergy (e.g., waveform) across to the secondary winding 38 b to theterminals 30 and 32 with high signal-to-noise immunity to common-modegenerated, spurious processing noise. In other words, the differentialRF drive output provides the common mode rejection and cancels spuriouscorruptive noise energy from altering the prescribed clinical treatmenttissue effect. This allows for the phase-correlated RF energy to beadjustable, providing potential for new control modes to dynamicallyalter in real-time the crest factor and other parameters of thedelivered RF waveshape within a given applied energy activation period.

The sense processor 36 is coupled to a voltage sensor 41 and a currentsensor 43. The voltage sensor 41 includes a resistor element 45 thatprovides an RF current weighted measurement of the delivered RF voltageto the terminals 30 and 32. A current transformer 47 then converts theweighted value of the RF voltage to provide a voltage sense signal tothe sense processor 36 for processing. The current sensor 43 similarlyprovides a current sense signal to the sense processor 36.

The sense processor 36 then transmits the voltage and current sensesignals to the controller 24, which adjusts RF output parameters inresponse to algorithm controls within a given RF activation period inreal-time. In particular, the controller 24 adjusts the amplitude,frequency, waveshape and time-dependent configuration of the RFarbitrary source 34 during the given RF activation period to deliver avariety of RF treatment modes. The treatment modes may include waveformshaving a duty cycle from about 5% to about 100% and may be eithercontinuous waves or variant duty cycle RF bursts, or alternate in singleor multiple combinations between modes to create a specific RF modesequence. In embodiments, the controller 24 is configured to control theRF arbitrary source 34, the RF amplifier 28 a and 28 b, and/or the HVPS27 in response to a selected electrosurgical operational mode, which maybe selected from a plurality of electrosurgical operational modes. Eachelectrosurgical operational mode may be associated with at least oneradio frequency input signal corresponding to a desired outputelectrosurgical waveform.

The controller 24 may include a microprocessor operably connected to amemory, which may be volatile type memory (e.g., RAM) and/ornon-volatile type memory (e.g., flash media, disk media, etc.). Thecontroller 24 may also include a plurality of output ports that areoperably connected to the HVPS 27 and the RF amplifiers 28 a and 28 ballowing the controller 24 to control the output of the generator 20.More specifically, the controller 24 adjusts the operation of the HVPS27 and the RF amplifiers 28 a and 28 b in response to a controlalgorithm that is implemented to track output of the RF amplifiers 28 aand 28 b to provide for sufficient power from the HVPS 27. Inparticular, as discussed in more detail below with respect to FIG. 4,the controller 24 supplies gain and phase control signals to each of theRF amplifiers 28 a and 29 b. In embodiments, a control algorithm mayalso inhibit or limit the output of RF amplifiers 28 a and 28 b to fitwithin the power supply limitations.

FIG. 4 illustrates the components of the RF amplifier 28 a. The circuitdesign of RF amplifier 28 b is substantially similar to the RF amplifier28 a, with the exception for the phase relationship, as discussed above,accordingly, only the RF amplifier 28 a is discussed. The RF amplifier28 a is a non-resonant multi-frequency transconductance amplifierconfigured to generate an RF current output for an applied RF voltageinput. The RF voltage input signal may have an arbitrary waveshape asprovided by the RF arbitrary source 34 as discussed above.

The RF amplifier 28 a is configured to operate with two RF control loops100 a and 100 b to control each of the components of an electrosurgicalwaveform, e.g., each half of an applied two-quadrant sinusoidal ornon-sinusoidal arbitrary RF signal input, having symmetric ornon-symmetric waveshape and variable timing, to address userconfigurable operating modes for achieving the desired clinical effect.RF control loops 100 a and 100 b are closed loop controlled RF channelswhere each positive or negative half of the applied sinusoidal input isprocessed independently. Control loop 100 a processes the negativehalf-cycle of the applied sinusoidal input, driving a power component102 a to create a positive half cycle source current at the primary side38 a of the patient isolation transformer 38. Control loop 100 bprocesses the positive half-cycle of the applied sinusoidal input,driving a power component 102 b to create a negative half cycle sourcecurrent at the primary side 38 a of the patient isolation transformer38. The power components 102 a and 102 b are shown as p-type and n-typemetal-oxide semiconductor field-effect transistors, respectively. Inembodiments, the power components 102 a and 102 b may be any p-type orn-type transistor, MOSFET, insulated gate bipolar transistor, (IGBT),relay, and the like. The patient isolation transformer 38 combines thedeveloped RF current from the RF amplifiers 28 a and 28 b at thesecondary winding 38 b to generate the arbitrary sinusoidal RF outputthat is the supplied to the terminals 30 and 32 for delivery to thetissue site.

Only the control loop 100 a is discussed in detail, since the controlloop 100 b is substantially identical with like components being labeledwith same identifiers having a letter “b.” The arbitrary RF signal fromthe RF arbitrary source 34 is applied at an input 104 of a phasecompensator 108. In addition, a phase control signal from the controller24 is applied at an input 106 at the phase compensator 108. The phasecompensator 108 establishes the output phase of the RF amplifier 28 a,which may be set to the desired phase (e.g., 0°) reference relative tothe applied arbitrary RF signal input 104 in response to the phasecontrol signal from the controller 24.

The phase compensator 108 provides a reference signal to an errorcorrection amplifier 110 a (or error correction amplifier 110 b) at apositive input 112 a. The error correction amplifier 110 a is configuredas an RF error correction amplifier that utilizes the reference signalat the positive input 112 a to control the output current, which issensed by an RF current sensor 116 a and supplied to a negative input114 a of the error correction amplifier 110 a. The error correctionamplifier 110 a outputs an RF control signal as a function of thereference signal and the detected output current. The RF current sensor116 a may be a current transformer, which may be a component of thecurrent sensor 43. The RF current sensor 116 a monitors the developed RFoutput current by converting the RF current to a signal voltage, whichis then returned to the negative input 114 a of the error correctionamplifier 110 a. A second frequency compensation network 126 a providesfrequency stability feedback compensation to the developed RF outputcurrent.

The first loop 100 a also includes a gain selector 118 a that provides again control adjustment to the output current control signal based onthe gain controls signal supplied by the controller 24. The gainselector 118 a is connected to the negative input 114 a of the errorcorrection amplifier 110 a and provides gain modification to the RFcurrent sensor 116 a. The gain selector 118 a is coupled to a firstfrequency compensating network 120 a, which is used by the errorcorrection amplifier 110 a to map the output current to the appliedreference voltage from the phase compensator 108. The frequencycompensating network 120 a provides stability corrected at the appliedfundamental operating frequency of the arbitrary RF signal input to thesensed return signal detected by the RF current sensor 116 a.

The error-corrected output signal of the error correction amplifier 110a is supplied to a gain amplifier 122 a, which is configured as an RFgain cell to provide a forward path gain for the error correction outputsignal. The output of the gain amplifier 122 a then drives the gate ofthe power component 102 a through a resistor element 124 a and RFcoupler components 128 a as the drive signal is elevated to theoperating voltage of the HVPS 27. RF coupler components 128 a mayinclude, but are not limited to, a capacitor, a transformer, an opticalcoupler, combinations thereof, and the like. The gain amplifier 122 aalso drives a second frequency compensating network 126 a to provide asecond level of frequency compensation for the developed RF outputcurrent.

The power component 102 a is shown as a MOSFET device having a gatecontact 134 a, a source contact 136 a and a drain contact 138 a. Thepower component 102 a presents a transconductance gain, converting thedrive voltage from the gain amplifier 122 a to an RF output current,which is applied to the primary winding 38 a. The power component 102 ais coupled to a resistor element 130 a at the gate contact 134 a and aresistor element 132 a at the +V HVPS power. The resistor element 130 aestablishes the DC bias operating level of the power component 102 a andthe resistor element 132 a provides source degeneration to the developedcurrent of the power component 102 a.

The RF amplifier 28 a also includes a stabilization amplifier 140, whichis configured as a DC stabilization amplifier for monitoring the outputDC voltage level generated by the output DC bias currents of the powercomponents 102 a and 102 b flowing into a shunted resistor element 142.The DC voltage through the resistor element 142 is maintained atapproximately 0 V DC by introducing steering error correction currents144 a and 144 b via the stabilization amplifier 140 to the resistorelements 130 a and 130 b, respectively.

The stabilization amplifier 140 also provides a DC bias set point thatestablishes a relative transconductance gain match between powercomponents 102 a (e.g., p-channel MOSFET) and power component 102 b(n-channel MOSFET), such that the positive and negative output peakcurrents delivered to the patient isolation transformer aresymmetrically balances over the minimum and maximum dynamic range of theoutput current signal level.

Conventional electrosurgical generators have a slower response time indelivery of RF energy to the tissue, which results in less than optimaltissue effect. In particular, the response is slowed by the high voltagepower supply, which controls the rate of change with which RF energy canbe delivered to the tissue site. In such designs, a controller initiallydrives the high voltage power source, which then drives the RF outputstage.

Further, conventional generators are based on various resonant outputtopologies. Resonant RF energy source operate at a unique switchingfrequency, which delivers both a fundamental RF operating frequency aswell as additional switching frequency harmonics. The harmonic frequencycomponents deliver an uncontrolled corruptive level of energy to thetissue, which may result in undesirable tissue effects. The harmonicfrequency components also increase the RF high frequency leakage presentin energy delivered to the patient.

Resonant-based RF generators also include reactive LC(inductor/capacitor) components to establish resonant operation. The LCcomponents act as energy storage components due to resonant switchingoperation and may also discharge the stored energy into the tissue,thereby also resulting in undesirable tissue effects.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

1-14. (canceled)
 15. A method for real time radiofrequency (RF) tissueenergy control comprising: generating a reference signal as a functionof an arbitrary RF signal from an RF arbitrary source and a phasecontrol signal; outputting a control signal as a function of thereference signal; and generating at least one electrosurgical waveformin response to the control signal.
 16. The method according to claim 15,further comprising: adjusting the control signal based on a gain controlsignal.
 17. The method according to claim 15, further comprising:supplying a current signal representative of the at least oneelectrosurgical waveform to at least one error correction amplifier. 18.The method according to claim 15, further comprising: injecting an errorcorrection current into the at least one electrosurgical waveform basedon a DC bias current.
 19. A method of generating an electrosurgicalwaveform comprising: generating a reference signal as a function of anarbitrary RF signal from an RF arbitrary source and a phase controlsignal; outputting a first control signal as a function of the referencesignal; generating a first component of the at least one electrosurgicalwaveform in response to the first control signal; outputting a secondcontrol signal as a function of the reference signal; generating asecond component of the at least one electrosurgical waveform inresponse to the second control signal; and adjusting at least one of thearbitrary RF signal and the phase control signal in response to at leastone selected electrosurgical operational mode.
 20. The method accordingto claim 19, further comprising: adjusting the first control signalbased on a first gain control signal; and adjusting the second controlsignal based on a second gain control signal.
 21. The method accordingto claim 19, further comprising: injecting an error correction currentinto the electrosurgical waveform based on a DC bias current.